Polymer networks swelling

The solvent in which the polymer network swelled is able to change the number of intermolecular bonds, to decrease observable flexibility of chain parts between points, and to stretch the system, i.e., to perform labor over it. Its influence on the Qon parameter, according to accepted approximations, is similar to the influence on the process in which only low-molecular compounds participate. Some deviation can be observed as a consequence of suppressing the solvent molecules in the network. One can find that the change of observable local rigidity of the chain as a consequence of network swelling is similar by its first approximation to its change for... 

Now, we turn to the case when one of the components of the mixed solvent in which the polymer network swells is polymeric [34, 35],... 

Polymeric systems displaying tunable and dynamic surface patterns are emerging as important platforms for many applications. Polymer networks swell and de-swell when exposed to a solvent. Controlling network heterogeneity enables to tune the... 

So-called soft contact lenses are actually made from a polymer hydrogel with a composition of up to about 50% water (the older hard lenses were a solid piece of plastic). If you are a contact lens wearer, you will know what happens when you leave a soft lens to dry out it shrinks and becomes hard like plastic. Dried up lenses will regain their former shape if soaked in water as the polymer network swells and refills with water. Some of the most current contact lens technologies, such as overnight or continuous wear lenses, are based on silicone hydrogels (polymers with a silicon backbone). 

The effect of the thermodynamic quality of solvent on the swelling kinetics of elastomeric polymer networks was theoretically and experimentally studied. Swelling is considered as a set of interrelated processes of diffusion and strain of a material. It is shown that the quality of a solvenf estimated by the Floiy-Huggins parameter value, significantly affects the nature of kinetic curves of polymer network swelling. 

These polymer networks swell in appropriate solvents, but do not dissolve. The degree of swelling strongly depends on the degree of cross-linkage. The lower the degree of cross-linkage, the more the gel swells. 

Microreticular Resins. Microreticular resins, by contrast, are elastic gels that, in the dry state, avidly absorb water and other polar solvents in which they are immersed. While taking up solvent, the gel structure expands until the retractile stresses of the distended polymer network balance the osmotic effect. In nonpolar solvents, little or no swelling occurs and diffusion is impaired. 

In one of these groups the polymer network consisting of synthetic and natural polymers is formed directly in the process of grafting. The degree of swelling is determined by the reaction condititions including the component ratio, initiation method, and ionogenic monomer content. 

A similar example is the formation of nonstoichiometric interpolymeric complexes between mutually complementary polyelectrolytes — polycation and polyanion [69,70], They behave like true polymer networks and are capable of swelling the interpolymeric complexes between PAAc and polyethylene piperazine swells, for instance, 16-18 times [70], Also advantageous in this case is the possibility to carry out this type of crosslinking in open systems, such as soil. 

Figure 11 Aqueous equilibrium swelling of cross-linked poly(A-isopropyl acrylamide-co-butyl methacrylate) as a function of temperature. Ww, Wp are the weight of water and polymer of swollen polymer network respectively. (From Ref. 32.)...

Product analysis polymer network s-NMR, gelation, swelling, birefringence, IR, NMR, STM, SANS, Brillouin scattering, pulse-propagation... 

The parameters of neutron scattering theory of polymer networks are A, the macroscopic stretching of the sample, or linear degree of swelling, f, the network functionality, K. which accounts for restricted junction fluctuations and a, a measure of the degree to which chain extension parallels the macroscopic sample deformation. The functionality is known from knowledge of the chemistry of network formation, and A is measured. Both K and a must be extracted from experiments. 

The presence of ionic moieties in hydrogels makes the theoretical treatment of swelling much more complex. In addition to the AGm xing and AGgiastic in Eq. (1), there is an additional contribution to the total change in Gibbs free energy due to the ionic nature of the polymer network, AG on c. 

So, interpenetrating polymer networks (IPNs) with a weight ratio of vinyl alcohol residue in PVA to acrylic acid monomer 4 6 exhibit positive swelling changes with temperature but IPNs 6 4 evidence negative swelling ones [48],... 

One of the widely used categories of polymers for biomaterials design is that of homo-or copolymers, which could generate hydrogels. Hydrogels are three-dimensional polymer networks that could swell in water without dissolution and that, due to their high water content and rubbery nature, are very similar to natural tissues and could be considered... 

VK Sarin, SBH Kent, RB Merrifield. Properties of swollen polymer networks. Solvation and swelling of peptide-containing resins in solid-phase peptide synthesis. JAm Chem Soc 102, 5463, 1980. 

Based on the solution property of poly (DMAEMA-co-AAm) in response to temperature, the temperature dependence of equilibrium swelling of poly (DMAEMA-c6>-AAm) gel as a function of chemical composition was observed as shown in Figure 6. The transition temperature of copolymer gel between the shrunken and swollen state was shifted to the lower temperature with increases in AAm content in the gel network. This is attributed to the hydrogen bond in the copolymer gel network and its hydrophobic contribution to the LCST Copolymer II gel was selected as a model polymer network for permeation study because it showed the sharp swelling transition around 34°C. 

Katono, H., Maruyama, A., Sanui, K., Ogata, N., Okano, T., and Sakurai, Y. Thermo-responsive swelling and drug release switching of interpenetrating polymer networks composed of poly(acrylamide-co-hutyl methacrylate) and polyfacrylic acid). J. Controlled Release 1991,16, 215-228. 

THE BERENS-HQPFENBERG MODEL. The Berens and Hopfenberg model considers the sorption process in glassy polymers as a linear superposition of independent contributions of a rapid Fickian diffusion into pre-existing holes or vacancies (adsorption) and a slower relaxation of the polymeric network (swelling).(lS) The total amount of sorption per unit weight of polymer may be expressed as... 

Interpenetrating polymer networks are defined in their broadest sense as an intimate mixture of two or more pol)Mners in network form [1,2]. Ideally, they can be synthesized by either swelling the first crosslinked polymer with the second monomer and crosslinker, followed by in-situ polymerization of the second component (sequential IPN s) or by reacting a pair of monomers and crosslinkers at the same time through different, non-interfering reaction mechanisms, simultaneous interpenetrating networks, SIN s. In fact, many variations of these ideas exist in both the scientific and the patent literature. In any case, at least one of the two components must have a network structure, as an IPN prerequisite. ... 

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